1. Field of the Invention
The invention is directed to an improved apparatus for generating a mixture of reducing agent and air.
2. Description of the Prior Art
One apparatus of this type with which this invention is concerned is known from the literature: Dieselmotor-Management [Diesel Engine Management], Vieweg Verlag, 2nd Edition, 1998, page 31. This apparatus is part of a system for posttreatment of exhaust gases of internal combustion engines, especially self-igniting internal combustion engines. By adding a reducing agent to the exhaust gas, the effectiveness of a reducing catalytic converter for reducing nitrogen oxides in the exhaust gas can be improved. The apparatus has a feed pump, by which reducing agent is pumped and which has a pump housing. The apparatus has also a mixing chamber, into which reducing agent and air pumped by the feed pump can be introduced, in order to create the mixture of reducing agent and air. The mixing chamber is embodied in a mixing chamber body, which is disposed separately from the feed pump. As a result, the apparatus has a large structural size, and a connecting line is necessary between the feed pump and the mixing chamber, which makes production and assembly of the apparatus complicated and expensive, and there is the risk of leaks at the connections of these elements. The known apparatus furthermore has a large idle volume filled with the reducing agent, which adversely affects the dynamics of the apparatus when there are changes in the required quantity of the mixture of reducing agent and air.